DSL vs. Cable vs. ISDN

Jun 17, 2000

Cruising the newsgroups all I hear is which is better? Cable or DSL. Well I am going to tell you!
Before we can go into which is better we are going to need to understand the two technologies. Here are the flavors of DSL:

ADSL - (Asymmetric Digital Subscriber Line) is the most popular form of DSL technology. ADSL is distance sensitive and performs betters when the consumer is within 12,000 feet from the Central Office. ADSL allows simultaneous voice and high-speed data data transmissions.

ADSL Lite - A lower data rate version of Asymmetric Digital Subscriber Line (ADSL)

IDSL - The always-on version of dial-up ISDN delivers symmeteric data at 144kps. Unlike other xDSL flavors this DSL technology does not allow you to upgrade beyond 144kps. IDSL is used because it offers customers higher bandwidth options for those who operate from distances up to 26,000 feet or more.

SDSL - Symmetric Digital Subscriber Line (SDSL) is a 2-wire implementation of (HDSL). Most reliable because it is has been a proven technology used by telephone companies for T1 internet access. SDSL or Symmetrical DSL, enables users to experience equal upstream and download speeds up to 1.5Mbps. Our SDSL services are packaged in bandwidth configurations ranging from 192Kbps, 384Kbps, 768Kpbs, 1.1Mbps, and 1.5Mbps. The distance from the central office will depend on the service speed you are able to receive.

CDSL - Consumer Digital Subscriber Line (CDSL) is a proprietary technology trademarked by Rockwell International.

EtherLoop - EtherLoop is currently a proprietary technology from Nortel, short for Ethernet Local Loop.

HDSL - High Bit-rate Digital Subscriber Line (HDSL) is generally used as a substitute for T1/E1.

RADSL - Rate Adaptive Digital Subscriber Line (RADSL) is any rate adaptive DSL modem, but may specifically refer to a proprietary modulation standard designed by Globespan Semiconductor.

VDSL - Very High Bit-rate Digital Subscriber Line (VDSL) is proposed for shorter local loops, perhaps up to 3000 ft.

Now, here a couple of differences in NORMAL DSL vs. Cable vs. ISDN:

Analog Modems

Analog modems use a telephone network as is. That is, there are no special provisions that are required to use analog modems in today's telephone networks. Analog modems simply allow digital data to flow over the telephone company's already analog network by performing a digital to analog conversion for transmission onto the network and vice versa on the receiving end. The only necessity for analog modems is that each end of the call must have a compatible modem. In essence, this makes analog modem connections the most ubiquitous form of data communications available today. However, analog modems are thus limited by the telephone company's voice bandwidth service. Current analog modems are struggling to achieve rates of only 56Kbps. With only a bandwidth of about 3,000 Hz, there is a extremely small finite limit on the amount of data that may be encoded and sent reliably through this network. User requirements far outstrip what analog modems can obtain today.


ISDN is a telephone company technology that provides digital service typically in increments of 64Kbps channels. ISDN has been around for many years, but it's popularity is now only beginning to increase due to the limitations of analog modems and the rise of Internet usage. ISDN requires the phone company to install services within their phone switches to support this digitally switched connection service. Roll out of this service initially got off to a slow start and was stalled by high costs, lack of standards and low acceptance rate by consumers.


DSL is technology is providing the next generation high bandwidth services to the home and business using the existing telephone cabling infrastructure. DSL to the home over existing phone lines promises bandwidths up to 1.5Mbps, but distance limitations and line quality conditions can reduce what will actually be achievable. DSL technologies will use a greater range of frequencies over the cable than traditional telephone services which in turn allow for greater bandwidth with which to send and receive information. (Back to Index)

Cable Modems

Cable modems are devices that attach to the cable TV network connection in a home. This broadband technology is being driven by the cable companies to provide services beyond traditional broadcast cable TV such as Internet access. Potential bandwidth estimates range upwards of 30Mbps from the service provider to subscriber. Cable modems are primarily used for consumer service. If cable is offered to your business, you should be aware of a few things. Cable networks are inherently different in design than telephone networks. Cable networks are broadcast oriented, meaning with each subscriber in an area receiving the same signals as all others in that area. xDSL is circuit oriented so that each connection is independent of all others. Cable services is a shared connectivity medium, very similar to a LAN, meaning the more users connected, the slower the connection speed will be. Cable is asymmetric, meaning upstream speeds are slow compared to the upstream speeds making it unsuitable for web hosting. Cable can also create serious security hazards due to the shared environment.

So you see all that the pros and cons are of the two technologies. DSL allows you to be always connected, doesn't take a phone line, and you will always get the same speeds they quote. Cable allows you to always be connected, depending on flavor, may use a phone line, speed will vary, but generally are faster than DSL.

Another big problem people will run into is MOST Cable modem providers will NOT provide a static IP. This means every time you reboot your PC you will get a new IP. That makes it VERY difficult to host a domain name off of a cable modem. ALOT of DSL providers DO give you a static IP. There are, of course, ways around the IP change problems. Companies like www.tzo.net and www.homeip.net provide free or pay for services to route your new IP to a domain name.

Another thing to think of is a business line. Most Cable providers WILL sell a person a business line. Up side of this is you will have your own pipe to the hub. This means you have effectively turned your cable modem into a DSL line. You will NOT have to share your bandwidth all the way to the box. You will NOT have to worry about people hacking into your machine because they are on the same line as you. You also will get faster speeds than a residential, always. But with this boost of features comes a boost of price. Expect the jump for the average 50/mnth to 150/mnth. For most though, this is DEFFIETLY worth it.

There you have it folks, all the data you need to know which to buy. (sorry ISDN.. seems you just suck)

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